Quick answer: Nail file grit measures how coarse a file is. The lower the number, the coarser the file, and the higher the number, the finer it is. Use 180 to 240 grit on natural nails. Use 100 to 150 grit only for reducing and shaping product such as builder gel, BIAB or gel, never on bare natural nails. A buffer, which is finer still, removes shine and smooths the surface before gel or BIAB. On a double-sided file like 100/180, each number is one side of the file.
Nail file grit chart
| Grit | Coarseness | Use it for | Safe on natural nails? |
|---|---|---|---|
| 80 | Very coarse | Heavy reduction of acrylic in salons | No |
| 100 | Coarse | Reducing builder gel and BIAB, filing off most of the product before a soak-off | No |
| 150 | Medium-coarse | Shaping and refining builder gel and BIAB | Not recommended |
| 180 | Medium | Shaping natural nail edges, refining gel and BIAB | Yes, with a light touch |
| 240 | Fine | Shaping natural nails gently, smoothing edges, removing scratch lines | Yes |
| Buffer | Very fine | Removing shine before gel or BIAB, smoothing ridges | Yes, lightly |
What does nail file grit mean?
The grit number describes the size of the abrasive particles on the file's surface. A low number means fewer, larger particles, which remove material quickly but leave deeper scratches. A high number means more, smaller particles, which remove less material and leave a smoother finish. That's why you work from coarse to fine: the lower grit does the heavy work, and the higher grit smooths away the scratch lines it leaves behind.
How to read a double-sided file
Most professional files have a different grit on each side, written as two numbers. A 100/180 file has a coarse 100 side for reducing product and a medium 180 side for refining. A 180/240 file has a medium side for shaping and a fine side for finishing. Many files are printed with the grit on each side, but if yours isn't, the rougher side is always the lower number.
Which grit should you use?
For natural nails: 180 to 240
Natural nails are made of thin layers of keratin, and a coarse file tears through those layers, leaving the edge rough, split and prone to peeling. Use 240 for gentle shaping and finishing, and 180 if you need to take off a little more length with a light touch. To shorten natural nails a lot, clip them first and then file, rather than filing down a long way with a coarse grit.
For prepping before gel polish or BIAB: a buffer
Before gel or BIAB, you only need to remove the shine from the nail surface so the base coat can grip. A soft buffer block does this without thinning the nail. Don't use a coarse file on the nail surface. If you can see dust and scratches, you're taking off too much. Our guide to nail prep explains the full routine.
For gel polish: 180 to 240, plus 100 for removal
Use 180 or 240 to refine the shape of a gel manicure. When it's time to take gel off, a 100 or 150 grit file quickly removes the shine of the top coat and some of the colour, so acetone can soak in faster. Stop before you reach the natural nail. See how to remove gel nail polish at home.
For BIAB and builder gel: 100 to 180, finishing with 240
BIAB and builder gel are much harder than natural nails, so they need a coarser grit to shape. Use 100 or 150 to reduce bulk and shape, 180 to refine, and 240 or a buffer if you want a smoother surface before top coat. For infills, a 100/180 file takes the old BIAB down quickly and then smooths it. Read how to infill BIAB at home.
Electric nail files
An electric nail file (e-file) uses interchangeable bits that come in different grits too, from coarse bits for reducing builder gel to fine bits for refining. It does the same jobs as a manual file much faster, but needs a light touch and practice. Read how to use an electric nail file.
How to file your nails properly
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File dry nails. Wet nails are softer and more likely to bend, split or peel when filed.
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Choose the right grit for what you're filing: 180/240 for natural nails, coarser grits only for product.
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Hold the file slightly under the free edge, and keep it level rather than tilted sharply up or down.
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File in one direction, from the side of the nail towards the centre, with long, light strokes. Sawing back and forth creates heat and frays the edge.
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Shape the tip first, then the sides. Don't file deep into the side walls, as that's where the nail gets its strength.
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Check every angle. Look from above, then turn your hand to check the nails from the fingertip side so they all match.
- Smooth the edge with a light pass of the finer side or a buffer, then finish with cuticle oil.
Choosing a shape? See our nail shapes guide for how to file each one.
Common filing mistakes
| Mistake | What happens | Fix |
|---|---|---|
| Using 100 grit on natural nails | Rough, split edges and thin nails | Use 180/240 on natural nails |
| Sawing back and forth | Frayed, peeling tips | File from the side to the centre in one direction |
| Filing wet nails | Bending and splitting | File only when nails are completely dry |
| Over-buffing before gel | Thin, sensitive nails | Buff lightly, just enough to remove the shine |
| Filing deep into the sides | Weak nails that snap at the corners | Keep the side walls straight and strong |
| Skipping the fine grit | Scratch lines that show through top coat | Finish with 240 or a buffer |
Looking after your nail files
Brush dust off your files after each use and clean them according to the type of file. Keep separate files for natural nails and for product if you can, so a worn, coarse file never ends up on your natural nails. Replace files when they feel smooth or stop removing product easily, as a worn file needs more pressure and creates more heat.
Nail files from Belle Beauty
Our nail files collection has professional double-sided files in 100/150, 100/180 and 180/240 grits, buffer blocks and an electric nail file. Every Belle Beauty gel, BIAB and builder gel kit also includes files and buffers, so if you're just starting out, see our nail kits.
Frequently asked questions
What grit nail file is best for natural nails?
180 to 240 grit. Use 240 for gentle shaping and finishing, and 180 if you need to remove a little more length.
Is a higher or lower grit nail file better?
Neither is better, as they do different jobs. Lower grits are coarser and remove product quickly. Higher grits are finer and give a smoother, gentler finish.
What does 100/180 mean on a nail file?
It's a double-sided file with a coarse 100 grit side for reducing product and a medium 180 grit side for refining.
What grit file should I use for BIAB?
100 or 150 to reduce and shape, 180 to refine, and 240 or a buffer to smooth before top coat.
Can I use a 100 grit file on natural nails?
No. 100 grit is too coarse for natural nails and can split, fray and thin them. Keep it for builder gel, BIAB and removing product.
What grit is a nail buffer?
Buffers are finer than files. They're used to remove shine and smooth the nail surface rather than to shape the edge.
Should you file nails in one direction?
Yes. Filing in one direction, from the side towards the centre, helps prevent splitting and peeling.
Should I file my nails wet or dry?
Dry. Wet nails are softer, so they bend and split more easily when filed.
